So I move some books from one shelf to another, to make room for the books on Bunyan (Hurrah for frolicking with the pilgrims!) - and I dislodge my copy of Witches Abroad. On picking it up, I sit cross-legged on the floor for a moment, reading the first two pages, and smiling. In the opening section, Pratchett waxes pseudo-philosophical on the nature of knowing, and the nature of stories.
"Oh blimey," sez I to the dog. "I'm writing "Witches Abroad: The Dissertation."